From Hydrated Ni₃(OH)₂(C₈H₄O₄)₂(H₂O)₄ to Anhydrous Ni₂(OH)₂(C₈H₄O₄): Impact of Structural Transformations on Magnetic Properties

Abstract

Dehydration of the hybrid compound [Ni3(OH)2(tp)2(H2O)4] (1) upon heating led to the sequential removal of coordinated water molecules to give [Ni3(OH)2(tp)2(H2O)2] (2) at T1 = 433 K and thereafter anhydrous [Ni2(OH)2(tp)] (3) at T2 = 483 K. These two successive structural transformations were thoroughly characterized by powder X-ray diffraction assisted by density functional theory calculations. The crystal structures of the two new compounds 2 and 3 were determined. It was shown that at T1 (433 K) the infinite nickel oxide chains built of the repeating structural unit [Ni3(μ3-OH)2](4+) in 1 collapse and lead to infinite porous layers, forming compound 2. The second transformation at T2 (483 K) gave the expected anhydrous compound 3, which is isostructural with Co2(OH)2(tp). These irreversible transitions directly affect the magnetic behavior of each phase. Hence, 1 was found to be antiferromagnetic at TN = 4.11 K, with metamagnetic behavior with a threshold field Hc of ca. 0.6 T. Compound 2 exhibits canted antiferromagnetism below TN = 3.19 K, and 3 is ferromagnetic below TC = 4.5 K.

Hybrid 2D Dual‐Metal–Organic Frameworks for Enhanced Water Oxidation Catalysis

“…As characterized by X‐ray diffraction (XRD), both the hybrid Ni‐MOF@Fe‐MOF and pristine Ni‐MOF share the same crystal phase with peaks assigned to (200), (−201), and (400) planes of a monoclinic structure (Figure d). As seen from the illustrated crystal structure (Figure S3, Supporting Information), Ni atoms are coordinated by six O atoms (µ 3 ‐OH and O in carboxylate) forming slightly distorted NiO 6 octahedra, which are further corner/edge connected with each other in the (200) planes resulting in 2D metallic layers separated by BDC ligands . In contrast, no distinct diffraction peaks can be observed for bare Fe‐MOF, suggesting its amorphous nature (Figure S4, Supporting Information).…”

Nickel Metal–Organic Framework Monolayers for Photoreduction of Diluted CO2: Metal‐Node‐Dependent Activity and Selectivity

“…Ni MOLs has been prepared by a traditional ultrasonication method, followed by a large amount water‐assisted freezing process to prevent MOLs from aggregating together, as illustrated in Figure a. The as‐prepared sample shares identical crystalline structure with the previously reported monoclinic Ni 2 (OH) 2 BDC MOF . The four diffraction peaks can be indexed to (200), (001), (201), and (−201) crystallographic planes, respectively, as shown in Figure b.…”

Hybrid interfaces in layered hydroxides: magnetic and multifunctional superstructures by design

“…The solid curves correspond to the parameterization of the experimental data using appropriate models. Reprinted with permission from [118]. Copyright 2014…”

“…A series of nickel compounds was obtained by François et al by dehydration of the hybrid compound [Ni 3 (OH) 2 (tp) 2 (H 2 O)4 ] (1),[118] whose structure is isotype to that of cobalt or nickel thiophene dicarboxylates described elsewhere [119,120]…”